1. Field of the Invention
The present invention relates to an image reading apparatus and method, and in particular, to an image reading apparatus and method which read a plurality of images recorded on a film.
2. Description of the Related Art
In image reading of a 135 size photographic film, in a case in which, even though an image frame which is supposed to be a leading frame is conveyed to a reading position, frame positions of subsequent frames are not defined, conveyance of the photographic film is stopped and an operator sets a leading frame position at the reading position manually.
Regarding technique relating to such positioning of an image frame, there is a technique in which positioning of a failure image frame, whose frame edge cannot be detected due to transmission density distribution being abnormal, is carried out by feeding a film with a determined amount. In this technique, a film conveying amount for the determined-amount-feeding is set on the basis of trends which are unique to the film being processed. To be more concretely, a trend of a size of the image frames which are photographed by a camera photographing images on the film is grasped by obtaining an average of image frame lengths (dimensions in a film conveying direction) L1n of all normal image frames, which are located in frontal position on the film with respect to the failure image frame which is to be positioned, is obtained. Further, a trend of a feeding pitch of the image frames of the camera is grasped by obtaining an average of dimensions L2n between the normal image frames. Thus, the film conveying amount for the determined-amount-feeding is set on the basis of the trends (sum of the average of L1n and the average of L2n). Therefore, in this technique, the positioning of the failure image frame can be positioned correctly compared to a case in which the film conveying amount is set to a predetermined amount based on the specification.
(refer to FIGS. 12 and 18 of Japanese Patent Application Laid-Open (JP-A) No. 5-142661)
However, in this prior technique, the above mentioned trends which are unique to the film cannot be grasped in a case in which the failure image frame is a leading image frame (a first image frame) of the film. Accordingly, in this case, the film is conveyed by a predetermined reference amount. Namely, it is necessary that an operator sets the leading image frame to the proper reading position manually after the film is conveyed by the predetermined reference amount.
Further, there is another technique in which, in a state in which at least one of an edge of an image frame at an upstream side in a conveying direction and an edge of the image frame at a downstream side in the conveying direction cannot be detected, a central position of this image frame is set on the basis of a central position of an image frame located at the downstream side, which has been already set, or on the basis of positions of a downstream side edge or an upstream side edge of an image located at the downstream side, which have been already set.
(refer to FIGS. 10 and 13 of Japanese Patent Application Laid-Open (JP-A) No. 2000-284377)
Further, in this prior reference, it is mentioned that, in a case in which an edge of a leading image frame is not clear, because positions of other image frames have not defined yet, it may be possible that a position of the leading image frame may be determined on the basis of a subsequent image frame whose edge is supposed to be detected by an optical sensor.
However, regarding positioning of the leading image frame whose edge cannot be detected at the reading position, even though the leading image frame may be defined, a concrete process or the like after the leading image frame is defined is not at all written in the Japanese Patent Application Laid-Open (JP-A) No. 2000-284377. Further, in a case of image reading of a film in which many image frames are subsequent from the leading image frame, whose frame edges cannot be detected and whose reading positions cannot be specified, further improvements must be needed.